The Quarterly journal of experimental psychology. B, Comparative and physiological psychology最新文献

The present experiments explored the importance of training with a common antecedent or consequence for common coding in symbolic matching-to-sample tasks with human subjects using reversal and transfer tests. Experiment 1 assessed common coding following training in many-to-one (MTO) and one-to-many (OTM) symbolic matching-to-sample tasks by comparing learning of partial and total reversals of these contingencies. Experiment 2 assessed common coding in MTO and OTM tasks by comparing performances in transfer tests when the common coding relations in the transfer phase were either consistent or inconsistent with those present during initial training. Evidence for common coding in the MTO and OTM discriminations was obtained in both experiments, although the amount of common coding was greater in the MTO discrimination in Experiment 1. These data are discussed in terms of associative mediational approaches to common coding phenomena. It is suggested that a basic requirement of an associative theory is that common coding should be more likely to occur when the stimuli are trained with a common consequence than when they are trained with a common antecedent, and that this requirement has been at least partly satisfied in the present studies.

Investigations of patterning discriminations by nonhuman animals have generally found that positive patterning is easier to learn than negative patterning. Studies of patterning discriminations in human causal learning tasks have failed to document any differences between positive and negative patterning. In the present study, human participants predicted an outcome on trials involving either a compound cue or its elements. Positive and negative patterning problems were successfully solved in a within-subjects design; negative patterning problems proved to be more difficult when an additional, 50% contingent cue was included (Experiment 2), but not when it was excluded (Experiment 1). Possible reasons for these results are discussed. The discussion concludes with an analysis of exemplar models (e.g., Pearce, 1994) of human causal learning and considers the conditions under which these models do and do not anticipate our results.

Presentation of unsignalled unconditioned stimuli (USs) interspersed among Pavlovian excitatory conditioning trials weakens conditioned responding to a target conditioned stimulus (CS; Rescorla, 1968). However, signalling these intertrial USs with another cue (a cover stimulus) has been shown to alleviate this degraded-contingency effect (e.g. Durlach, 1982, 1983). In contrast to signalling the intertrial USs, the present experiments examined the effect on the degraded-contingency effect of signalling the target CS-US pairings. Experiment 1, using parameters selected to avoid overshadowing, found that consistently presenting a cover stimulus immediately prior to the target CS-US pairings during degraded-contingency training alleviated the degraded-contingency effect. Experiment 2 examined the underlying mechanism responsible for this cover-stimulus effect through posttraining associative inflation of the cover stimulus or the context, and found that inflation of the cover stimulus attenuated responding to the target CS (i.e. empirical retrospective revaluation). The results are discussed in terms of various acquisition- and expression-focused models of acquired responding.

Learning that one cue (CS) predicts a second, salient cue (US) can often be slowed by prior exposure to one or both stimuli. In animals, CS-US learning is more strongly retarded following uncorrelated exposure to both CS and US than following exposure to the US alone. In this paper we present several studies showing a similar effect in humans, using a computer-based task. Experiments 1 and 2 used a between-groups design and demonstrated a strong CS/US exposure effect, whether or not the US was signalled by a neutral cue during exposure. Experiment 3 demonstrated similar effects using a within-subjects design. Overall, these results are consistent with several theoretical interpretations and suggest that uncorrelated CS/US exposure leads to a robust retardation of subsequent CS-US learning in humans.

In each of two experiments rats were preexposed to four compound landmarks (AX, BX, CX, and DX) one at a time; they were then trained to find a submerged platform located in a fixed position in a swimming pool using these same landmarks. When the preexposure was SHORT (4 sessions) it facilitated subsequent learning (a perceptual learning effect), whereas when rats were given a LONG preexposure phase (8 sessions) this facilitatory effect disappeared. EXTRA-LONG preexposure (16 sessions) reversed the facilitatory effect--that is to say, we observed retarded learning. The results show that rats' ability to navigate towards an invisible goal is affected by the length of their preexposure to the spatial cues that signal the location of the goal. These data are consistent with an associative analysis of the swimming pool navigation task.

Four experiments using a conditioned lick suppression preparation with rats were conducted to examine whether overshadowing of subsequent events could be obtained in Pavlovian backward conditioning (i.e. unconditioned stimulus [US] before conditioned stimulus [CS]), and to determine whether such overshadowing could be reversed without further training with the overshadowed CS, as has been reported in overshadowing of antecedent events. In Experiment 1, a backward-conditioned CS overshadowed a second backward-conditioned CS. Two posttraining manipulations, extinction of the overshadowing CS (Experiment 2) and shifting of the temporal relationship of the overshadowing CS to the US (Experiment 3), increased responding to the overshadowed CS. These results constitute the first unambiguous demonstration of stimulus competition between subsequent events using first-order conditioning, and they show that, like overshadowing with forward conditioning, such overshadowing is due, at least in part if not completely, to a failure to express information that had been acquired.

Five appetitive conditioning experiments with rats examined the ability of extinction cues (ECs) to reduce spontaneous recovery after extinction procedures that varied the temporal relation between the ECs and the conditioned stimulus (CS) and included presentations of additional events (e.g. other stimuli correlated with extinction, CSs, and the US). In extinction, two different ECs were presented either closely in time before (i.e. recent to), or more distant (i.e. remote) from a nonreinforced CS. Both recent and remote ECs reduced spontaneous recovery to the CS when present during testing (Experiments 1-4). Each EC reduced recovery despite the addition during extinction of a second EC and CS (Experiments 1, 3, and 4), and the US (Experiment 3). Experiments 4 and 5 investigated the recent and remote ECs' tendency to control a serial occasion setting discrimination involving the target CS under explicit training conditions. Neither EC gained such discriminative control. Possible explanations of the results are discussed, including configural learning, occasion setting, and contextual cue control.

In three experiments, participants learned which of a variety of foods were capable of causing an allergic reaction in a hypothetical patient during training in which a compound of a treatment and a target food cue was paired with the reaction. In Experiment 1 the causal ratings of the target cue were increased if the treatment cue was pretrained as a preventative cause of the reaction. Experiments 2 and 3 demonstrated that the magnitude of this super-learning is unaffected by the order of compound and treatment cue training. The final study also showed that forward super-learning is not induced solely by simple exposure to the treatment cue prior to compound training but, rather, depends upon training the treatment cue as a preventative cause, whereas retrospective super-learning may be due merely to exposure of the treatment cue. These results are problematic for contingency-based accounts of causal induction but accord with modified and extended associative theories.

Any occasion on which an animal is placed in an experimental setting or context and receives pairings of one event with another provides the opportunity for a variety of associative structures to be acquired. These structures range from simple associations, which allow the presentation of one event to activate or prime a memory of the other, to hierarchical associations, which allow a simple association to be primed by some other event (e.g. the context in which the simple association was acquired). Experiments with rats that reveal priming effects consistent with both of these putative associative structures are reviewed.